A wireless device (e.g., a cellular phone or a smartphone) in a wireless communication system may transmit and receive data for two-way communication. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to generate a modulated RF signal, amplify the modulated RF signal to generate a transmit RF signal having the proper output power level, and transmit the transmit RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may amplify and process the received RF signal to recover data sent by the base station.
The transmitter and the receiver of the wireless device may include a plurality of amplifiers. In one example, the transmitter may include a driver amplifier to amplify the modulated RF signal. In another example, the receiver may include a low noise amplifier to amplify a RF signal received from another wireless device. In some wireless devices, the output signal of an amplifier may interfere with an operation of another module within the wireless device. For example, the output signal of the driver amplifier may amplify a modulated RF signal having a F0 (e.g., 2.4 GHz) carrier frequency. The output signal of the driver amplifier may include an unwanted signal with a frequency associated with a second harmonic (2F0) of the modulated RF signal (e.g., a 4.8 GHz signal). If the wireless device includes a local oscillator that generates a 4.8 GHz signal (e.g., for upconverting signals to and/or for downconverting signals from a wireless signal having a 2.4 GHz carrier signal), then the second harmonic of the modulated RF signal may interfere with the operation of the local oscillator.
Thus, there is a need to improve the amplification of signals and attenuate unwanted signals associated therewith to improve the performance of the wireless device.